Method No1 :-

MTK Engineering Mod Trick :-

1) After That Download MTK Engineering Mod Apk From Play store.

2) Open The App  An Select Prefer Network.

3) Now Select LTE/GSM/WCDMA & Save It.

4) Wait For Few Second & You Device Take Jio Network.

Method No2 :-

Coustom Rom Install Trick :- 

Remember (We Are Not Responseble For Any Kind Off Issues Try This Trick In Your Own Risk.)

1) Root Your Device & Install Recovery Mod In You 3G Device.

2) Now Download 4G Coustom Rom From By Google Search. ( You Can Search As Download 4G Coustom Rom)

3) After Download & Install You Will See A New Network Settings Option. Select LTE Or 4G.

4) Enjoy 4G.

Method No3 :-

Xposed Framework Install Trick :-

1) Download Both App Xorwar 2G/3G/4G Switcher & Xorwar 2G/3G/4G Interface App.

2) Open The App & Select Network Settings Option.

3) Select 4G/ LTE Network.& Apply The Settings.

4) Restart Your Device & Start Internet.